Same IP Address Why?

I have wireless connection on my laptop and also have a desktop computer in same internet connection. When I check my systems IP address from http://whoisthisip.com this site, it shows the same IP address for both laptop & desktop. why?

Because it is reporting the ip-address give your router by the ISP. The whole point for have a router is to create a LAN where each computer/device has a unique ip address that is then mapped on the public WAN address - - this is the NAT feature